Kanon has been so swept up in the discovery of the depths of her feelings for Saki that she hasn’t had the time to consider all the implications. Even beginning with what it means for her own sexuality, much less how her family, friends and society in general would react to her being in love with another girl.
On that note, I’ve seen some people refer to Kanon as bisexual despite the lack of evidence. Kanon herself made a point to clarify there is a distinct difference between fangirling over an actor, or admiring a teacher who treated her fairly, as compared to having a crush on a celebrity or teacher. Not to mention, there was once a guy who got close to Kanon for much that same reasons as Saki, yet she still rejected him. Of course, not is also not conclusive evidence that she can’t be attracted to members of the opposite gender, just that it’s never happened, so for now I’ll refer to Kanon not as a lesbian, but as a Sakisexual.